Although the pathogenesis of Hodgkin's disease is not clear, molecular analyses revealed characteristic features which proved the clonal origin of the disease. EBV injection can be demonstrated in more than 50% of cases at the DNA or protein level. Recently, immunoglobulin gone rearrangements were found in single Hodgkin and Reed-Sternberg cells. These rearrangements may be used as defined markers to detect residual disease after chemotherapy. This is of importance for the treatment of advanced stages, since about 50% of patients in this group will not be cured, and attempts are made to improve treatment results by high-dose chemotherapy. Salvage therapy for relapsed patients including high-dose chemotherapy with autologous stem cell support frequently results in remission although duration is generally short. New immunotherapy strategies with immunotoxins or bispecific antibodies are currently analyzed in clinical studies.